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PerformanceChecked through WebDiag API

CSS Delivery Analyzer

The tool parses stylesheet links and inline style blocks, safely fetches a bounded CSS set, and reports decoded samples, @import, @font-face, MIME, compression, cache, and delivery errors.

  • Up to 16 unique stylesheets
  • External + inline CSS
  • No unused-CSS claims
Online tool

Try the tool

Enter a URL: WebDiag will run a safe network check and show the result.

Page URL

Network check through backend

For HTTP/SEO tools, the URL is sent to the WebDiag API, where SSRF protection, DNS/IP policy, and redirect limits are applied.

Reviewed: 2026-07-17
01

How to use it

  1. 1

    Paste a public HTML page URL.

  2. 2

    WebDiag discovers stylesheet links and inline style blocks, then fetches a bounded CSS sample.

  3. 3

    Review duplicate links, @import chains, decoded bytes, MIME, compression, and failed stylesheets.

02

What the tool can do

  • Same-host/cross-host inventory and media/alternate/disabled signals.
  • Counts inline bytes, sampled decoded bytes, @import, and @font-face.
  • Checks response status, text/css MIME, Content-Encoding, Cache-Control, and redirects.
03

Common use cases

  • Find duplicate stylesheet requests and MIME errors.
  • Check for @import discovery chains.
  • Review the bounded decoded CSS surface after a release.
04

How it works inside

Every CSS URL is revalidated by the public-target policy and bounded decoded-body limit.

The sampled size is not a browser transfer waterfall or an unused-CSS measurement.

05

Questions and answers

Does the tool identify render-blocking CSS?

It shows default-media candidates and loading attributes but does not claim runtime blocking without a browser trace.

Why is @import treated as a review signal?

It can create an additional discovery chain. The actual impact depends on order, cache, and browser runtime.